In the above-cited U.S. Pat. No. 5,063,654, there is disclosed a method of making an amorphous steel transformer core that involves making up packets of amorphous steel strip and then wrapping these packets about an arbor to build up a core form. When the core form is removed from the arbor, it has a window where the arbor was located, and the packets surround this window. Each packet comprises a plurality of superposed groups of amorphous steel strip, and each group comprises two superposed sections, each of which comprises many thin layers of strip.
Each multi-layer section of strip is derived from composite strip comprising many thin layers of strip disposed in superposed relationship. The composite strip is cut into sections of controlled length, the layers in each section having transversely-extending edges at their opposite ends and a length dimension measured between said transversely-extending edges at opposite ends. Each group is assembled by stacking two of these sections together. In U.S. Pat. No. 5,063,654 the two sections forming a given group are cut to the same length and are stacked together with the transversely-extending edges of their layers at each end in alignment, thus forming a group that has squared-off edges at its opposite ends.
When the above-described group of U.S. Pat. No. 5,063,654 is wrapped about the arbor of a core-making machine to produce a core form, the transversely-extending edges of the layers at one end of the group are maintained in substantial alignment, thus retaining the substantially squared-off edge at one end of the group. But at the other end of the group, the transversely-extending edges of the layers become staggered as a result of the larger circumference of the core form at the outer layers compared to that at the inner layers. As a result of this staggering, the edge of the group is forced into a beveled configuration, as shown at 52 in FIGS. 1 and 2 of the present application.
I have found that this beveled configuration is disadvantageous from a core-loss viewpoint, whether the joint is a lap-type joint or a butt-type joint. In the case of the lap joint, where the ends of each group overlap to form the lap joint, this beveled configuration appears to introduce a thinness in the magnetic circuit at a crucial location where steel is needed to produce ideal flux transfer. In the case of the butt joint, the beveled configuration introduces a relatively large V-shaped gap between the substantially-aligned, transversely-extending edges of the group, which gap detracts from ideal flux transfer between the aligned ends.